WHITE WESTINGHOUSE DAYTONA 837 Chassis Formenti F8 Detailed Viewing.

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Supply with TDA4601 (Siemens)

TDA4601 Operation.

* The TDA4601 device is a single in line, 9 pin chip. Its predecessor was the TDA4600
device, the TDA4601 however has improved switching, better protection and cooler running.

The (SIEMENS) TDA4601 power supply is a fairly standard parallel chopper switch mode type,
which operates on the same basic principle as a line output stage. It is turned on and off by a
square wave drive pulse, when switched on energy is stored in the chopper transformer
primary winding in the form of a magnetic flux; when the chopper is turned off the magnetic
flux collapses, causing a large back emf to be produced. At the secondary side of the chopper
transformer this is rectified and smoothed for H.T. supply purposes.
The advantage of this type of supply is that the high chopping frequency (20 to 70 KHz
according to load) allows the use of relatively small H.T. smoothing capacitors making
smoothing easier. Also should the chopper device go short circuit there is no H.T. output.


In order to start up the TDA4601 I.C. an initial supply of 9v is required at pin 9, this voltage
is sourced via R818 and D805 from the AC side of the bridge rectifier D801, also pin 5
requires a +Ve bias for the internal logic block. (On some sets pin 5 is used for standby
switching). Once the power supply is up and running, the voltage on pin 9 is increased to 16v
and maintained at this level by D807 and C820 acting as a half wave rectifier and smoothing
circuit.

PIN DESCRIPTIONS
Pin 1 This is a 4v reference produced within the I.C.
Pin 2 This pin detects the exact point at which energy stored in the chopper transformer
collapses to zero via R824 and R825, and allows Q1 to deliver drive volts to the
chopper transistor. It also opens the switch at pin 4 allowing the external capacitor
C813 to charge from its external feed resistor R810.
Pin 3 H.T. control/feedback via photo coupler D830.
The voltage at this pin controls the on time of the chopper transistor and hence the
output voltage. Normally it runs at Approximately 2v and regulates H.T. by sensing a
proportion of the +4v reference at pin 1, offset by conduction of the photo coupler
D830 which acts like a variable resistor. An increase in the conduction of transistor
D830 and therefor a reduction of its resistance will cause a corresponding reduction
of the positive voltage at Pin 3. A decrease in this voltage will result in a shorter
on time for the chopper transistor and therefor a lowering of the output voltage and
vice versa, oscillation frequency also varies according to load, the higher the load the
lower the frequency etc. should the voltage at pin 3 exceed 2.3v an internal flip
flop is triggered causing the chopper drive mark space ratio to extend to 244 (off
time) to 1 (on time), the chip is now in over volts trip condition.
Pin 4 At this pin a sawtooth waveform is generated which simulates chopper current, it is
produced by a time constant network R810 and C813. C813 charges when the
chopper is on and is discharged when the chopper is off, by an internal switch
strapping pin 4 to the internal +2v reference, see Fig 2.
The amplitude of the ramp is proportional to chopper drive. In an overload
condition it reaches 4v amplitude at which point chopper drive is reduced to a
mark-space ratio of 13 to 1, the chip is then in over current trip.

The I.C. can easily withstand a short circuit on the H.T. rail and in such a case the
power supply simply squegs quietly. Pin 4 is protected by internal protection
components which limit the maximum voltage at this pin to 6.5v.
Should a fault occur in either of the time constant components, then the chopper
transistor will probably be destroyed.
Pin 5 This pin can be used for remote control on/off switching of the power supply, it is
normally held at about +7v and will cause the chip to enter standby mode if it falls
below 2v.
Pin 6 Ground.
Pin 7 Chopper switch off pin. This pin clamps the chopper drive voltage to 1.6v in order to
switch off the chopper.
Pin 8 Chopper base current output drive pin.
Pin 9 L.T. pin, approximately 9v under start-up conditions and 16v during normal running,
Current consumption of the I.C. is typically 135mA. The voltage at this pin must
reach 6.7v in order for the chip to start-up.




- Line deflection output (S2000)

- Frame deflection output TDA3653 (PHILIPS)

- Chroma + Luminance with TDA3562A (PHILIPS)

- IF + Synchronization with TDA4502A (PHILIPS)

- Tuner

- Audio Unit

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TDA3562A

PAL/NTSC ONE-CHIP DECODER
DESCRIPTION


The TDA3562A is a monolithic IC designed as
decode PAL and/or NTSC colour television standards
and it combines all functions required for the
identification and demodulation of PAL and NTSC
signals.


.CHROMINANCE SIGNALPROCESSOR

.LUMINANCE SIGNAL PROCESSING WITH
CLAMPING

.HORIZONTAL AND VERTICAL BLANKING
.LINEAR TRANSMISSION OF INSERTED
RGB SIGNALS
.LINEAR CONTRAST AND BRIGHTNESS
CONTROL ACTING ON INSERTED AND MATRIXED
SIGNALS
.AUTOMATIC CUT-OFF CONTROL
.NTSC HUE CONTROL